It is known to use artificial structures to assist muscular contraction. Such structures are adapted to assist atrial or ventricular contraction, or to assist or replace a natural sphincter. The use of such artificial sphincters increases currently because the faecal and urinary incontinences affect now 10% of people over 60 years of age and dramatically increase over 80. Several pharmaceutical or surgical solutions have been developed for treating incontinence. Generally, the outcome of surgery for treatment of urinary and faecal incontinence has to be regarded as low. The impacts on health care costs and overall quality of life of the patient are enormous.
The AMS800 artificial sphincter for urinary incontinence is commercialized by American Medical Science and is composed of three components, a cuff, a pump, and a pressure-regulating balloon. The cuff is implanted at the bulbous urethra in males and is inflatable by means of a fluid. The pump is implanted in the scrotum and the pressure-regulating balloon is implanted in the abdomen. The major problems when using AMS800 is the tissue erosion around the urethra due to the constant pressure, the atrophy and irritation of tissues at the location of the inflatable cuff, and the emergency surgery for repair as the device stays in close position in the event of mechanical failure. All commercialized artificial sphincters whether for urinary or feacal incontinence bear the same drawbacks.
The ProAct artificial sphincter for urinary incontinence is commercialized by Uromedica and is composed of two small implantable balloons. During a short outpatient procedure, the balloons are surgically placed under the skin in the area where the prostate of the patient was surgically treated. The balloons help protect against accidental leaking of urine by increasing the amount of pressure required to urinate. When the patient need to urinate, a normal amount of effort still should be required to push the urine out. However, the pressure from the balloons will help guard against unintentional urine loss, such as during a sneeze or cough. The major problems when using ProACT are identical to the problems using AMS800 artificial sphincter described above.
Some publications describe the use of artificial sphincters comprising shape memory alloy elements suitable for opening and closing a part of an organ in a living body. EP 1 238 638 describes an artificial sphincter having an opening/closing portion for opening and closing, wherein said opening/closing portion has:                a pair of elongated shape memory alloy elements that change reversibly between opposite shapes upon changes in temperature, and        hinges that link said pair of shape memory alloy element together in a cylindrical shape.        
Such artificial sphincter is placed around the intestine of a human or animal inside the body near to an intestinal opening so that the opening/closing portion constricts the intestine. When the shape memory alloy elements are heated, they change shape, so that the constricting force on the intestine is lost.
However, as the opening/closing portion is still constricting the same region of the intestine, there is a damage to this part of the body, and more especially a risk of tissue erosion, atrophy and burns, due to the constant pressure and heating of the shape memory alloy elements.
Reversible thermal lesions occur when the local temperature is increased to the 42° C. to 44° C. range (5 C-7° C. over the normal body temperature of 37° C.) and that irreversible thermal lesions occur when the local temperature is increased above 45° C. (>8° C. temperature rise over normal).
Moreover, in normal state, the shape memory alloy elements are not heated and are each bent to constrict the intestine. That means that heating is necessary to open the artificial sphincter. If the heating means fail, the sphincter remains closed and cannot be open what may be leading to life threatening complications. A surgery is then necessary to open the artificial sphincter and solve the problem.
Another artificial sphincter has been proposed in JP 07-051304. This document describes a constrictor comprising two shape memory alloy elements with different shape memories, and covered by covering materials. The first covering material is formed in a shape to close the urethra in the daytime, and the second covering material is formed in a shape to half closed the urethra in the night. This sphincter allows to change the pressure to the urethra, in order to prevent the incontinence in life action in the daytime, and to avoid necrosis of the tissue by loosing the pressure to the urethra in the night.
However, the drawbacks of such artificial sphincter are that there is a risk of necrosis and consequential tissue erosion, due to the constant pressure to the urethra during the day and that there is a risk of incontinence during the night.
Therefore there are, at the present time, no adequate solutions, whether commercial or in the literature, for implanting artificial contractile structures, particularly for the treatment of faecal or urinary incontinence.